The present invention relates to systems using cleaning bodies, generally sponge balls, for cleaning the pipes of heat-exchangers and, in particular, it concerns a ball trap for removing the cleaning bodies from the main fluid flow path of the system, such ball trap having a safety-release sieve gate.
It is known to introduce into water about to pass through a heat exchanger cleaning bodies whose function it is to wipe clean the heat exchange surfaces of the condenser.
When cleaning is accomplished by the use of such cleaning bodies, they must be captured, or recovered, from the water downstream of the heat exchanger. After such capture, the cleaning bodies are recirculated to a location upstream of the condenser to be re-introduced in to the cooling water. Hereinafter, the cleaning bodies are referred to as cleaning balls, the composition of which is not the concern of the application.
It is known to provide a ball trap that includes a grate, screen, sieve or grid, hereinafter referred to as a sieve, with a bar spacing less than the diameter of the balls, in the path of the water downstream of the condenser to recover the cleaning balls. Also included is a means by which the captured balls are removed from the downstream pipe so as to be collected and thereafter re-introduced upstream as necessary.
Various ball trap formations have been suggested. Generally, the ball traps of the prior art include sieves deployed solely within the diameter of the pipeline. The sieve is usually deployed at an angle to the direction of the fluid flow path such that the cleaning balls are forced along the face of the sieve to a collection point from which the cleaning balls are removed form the downstream pipe. Representative of these ball traps are U.S. Pat. No. 5,010,950 to Voith, U.S. Pat. No. 4,620,589 to Koller, U.S. Pat. No. 4,539,115 to Patzig, and German Patent No 3,411,461 to Grewe.
An issue confronted by the ball traps of prior art is that of micro or biological foulant build-up on the sieve. This can restrict the flow of cooling fluid through the sieve and cause increased pressure of the upstream side of the sieve. Some systems of the prior art monitor the pressure on both sides of the sieve and when the differential pressure reaches a preset limit, the sieve is displaced, usually rotated, so as to open the pipeline to unrestricted flow. Such displacement may be in response to an emergency situation or to perform a backwash so as to clear the foulant from the sieve.
Since the sieve is deployed within the pipeline, the surface area of the sieve is limited by the diameter of the pipe and the deployment angle of the sieve within the pipe. Generally, the sieves of prior art are elliptical or partially elliptical having surface areas of not more than about 200–250 percent of the cross-sectional area of the pipeline.
An alternative to the ball traps of prior art is offered in U.S. Pat. No. 5,450,895 to the present assignee. U.S. Pat. No. 5,450,895 discloses a ball trap with a sieve “tube” deployed within a portion of the main pipeline and extending out of the main flow path of the cooling fluid. The sieve of U.S. Pat. No. 5,450,895 provides a larger sieve surface area. U.S. Pat. No. 5,450,895 relates to systems having relatively small pipeline diameter such as many common industrial applications, but is unsuitable for high flow rate systems having large diameter pipeline, such as power station cooling system, because it lacks the pressure release feature required in such systems.
There is therefore a need for a ball trap with a sieve having a surface area greater than or equal to 300 percent of the cross-sectional area of the pipeline, the sieve including a safety-release sieve gate, which when open allows unrestricted flow of cooling fluid.